If you increase the input signal level for the receiver 2 spec (0.5uV) to the level used in the Receiver 1 spec (1.5uV), thatwould be an increase of 20 log ( 1.5 / 0.5 ) = ~10 dB. One might then hope that the S/N would also increase by 10 dB,making it 16 dB for Receiver 2 vs. 10 dB for Receiver 1.

While it isn't a perfect comparison, and I'm often suspicious of how closely receivers actually meet their specifications,that would imply that Receiver 2 is somewhat more sensitive than Receiver 1.

In practice I find that the usefulness of a receiver often depends on other factors. For example, the sensitivity of some2m ham rigs when listening on Aircraft AM band is rather poor. In practice when we have tried to use them to listen foran ELT, most were swamped by a local FM station whose image fell on 121.5 MHz.

You really have to compare them against the same signal to seefor yourself.

Because aircraft signals can carry for long distances at altitude,many aircraft transceivers are actually less sensitive than theymight be, on the assumption that they are most interested inrelative strong local signals from a nearby airport rather thanducted interference from a more distant one: this would particularlybe the case for a low power transmitter like an HT. We saw this whenwe converted some old 100kHz spacing aircraft radios for use asELT monitors: a preamp brought them up to "normal" receiversensitivity.

So there isn't necessarily anything wrong with the aircraft bandtransceiver: the receiver sensitivity is probably appropriate forthe expected range and output power of the station to whomthey are talking.

It is likely that the aviation receiver has bandpass filters to protect the RF preamplifier from out of band signals. This adds the loss of the bandpass filter to the noise figure of the preamplifier so the radio is less sensitive. But, in practice, since there are strong transmitters everywhere--like the cell phone transmitter at your waist--this tradeoff is quite worthwhile if you want a reliable radio that isn't disturbed by nearby out of band transmitters.

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